import java.util.Deque;
import java.util.LinkedList;
import java.util.Stack;

public class BinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用
        public TreeNode(char val) {
            this.val = val;
        }


    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode root = new TreeNode('A');
        return root;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root == null){
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null){
            return;
        }
        preOrder(root.left);
        System.out.print(root.val+" ");
        preOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null){
            return;
        }
        preOrder(root.left);
        preOrder(root.right);
        System.out.print(root.val+" ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root == null){
            return;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if(root == null){
            return 0;
        }
        return size2(root.left)+size2(root.right)+1;

    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root == null){
            return;
        }
        if(root.left==null&&root.right==null){
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if(root==null){
            return 0;
        }
        if(root.left==null&&root.right==null){
            return 1;
        }
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);

    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(root ==null){
            return 0;
        }
        if(k==1){
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right,k-1);

    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if(root == null){
            return 0;
        }
        int lefthight = getHeight(root.left);
        int righthigjht = getHeight(root.right);
        return Math.max(lefthight+1,righthigjht+1);
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root == null){
            return root;
        }
        if(root.val == val){
            return root;
        }
        TreeNode ret1 = find(root.left,val);
        if(ret1!=null){
            return ret1;
        }
        TreeNode ret2 = find(root.right,val);
        if(ret2!=null){
            return ret2;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if(root == null){
            return;
        }
        Deque<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode cur = queue.poll();
            System.out.println(cur.val);

            if(cur.left != null) {
                queue.offer(cur.left);
            }
            if(cur.right != null) {
                queue.offer(cur.right);
            }
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root == null){
            return  false;
        }
        Deque<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode cur = queue.poll();
            if(cur==null){
                break;
            }
            System.out.println(cur.val);
            queue.offer(cur.left);
            queue.offer(cur.right);

        }
        while (!queue.isEmpty()) {
            //一个元素 一个元素 出队来判断 是不是空
            TreeNode tmp = queue.peek();
            if(tmp == null) {
                queue.poll();
            }else {
                return false;
            }
        }
        return true;
    }
}